A plenoptic camera (light field camera) is a camera which is capable of sampling a light distribution and light directions in a light field. On the basis of this information, images can be collected with increased focal depth and/or images can be digitally refocused. In a standard plenoptic camera, an array of microlenses is placed in front of the image plane as, for example, a photographic plate or a photosensor array. This construction not only records the light focused onto the particular plane but records the field of light rays (light field) emanating from the lens. The final image can be generated from the recorded raw data using a computational algorithm, which is why the plenoptic camera is regarded as belonging to the field of computational photography. There exist algorithms to generate images from the light field at different (virtual) focal planes and to estimate the scene depth at multiple positions.
The two plenoptic camera designs published previously are:
1. The standard plenoptic camera first described by Lippmann in 1908, which is also described in WO 2007/092581 A2 and by Ren Ng et al. in “Stanford Tech Report” CTSR 2005-02. The effective resolution of this plenoptic camera is the same as the number of microlenses used.2. The “focused plenoptic camera” first described in 2008 in a technical report by Lumsdaine and Georgiev (A. Lumsdaine and T. Georgiev. Full resolution lightfield rendering. Technical report, Adobe Systems, January 2008) and US 2009/0041448 A1. The design described in these publications achieves a higher effective resolution. However, no theory has been presented, which allows for an analytic calculation of the achievable effective resolution of a plenoptic camera. Furthermore, the conventional image rendering algorithm works by transforming the image to the frequency domain.
A modified plenoptic camera and associated algorithms are described in WO 2006/039486 A2. As with the standard techniques, this plenoptic camera comprises a main lens, a microlens array and a photosensor array having a finer pitch than the microlens array. The microlens array being arranged in the focal plane of the main lens may comprise microlenses with different sizes being selected such that light through one of the microlenses does not overlap light through other of the microlenses. Although a locally varying angular resolution can be obtained with the different microlenses, the focal points of all microlenses share a common plane (plane of photosensor array), i.e. all microlenses of the conventional plenoptic camera have the same focal length for imaging a virtual image at an infinite distance. Thus, the imaging properties of the plenoptic camera described in WO 2006/039486 are essentially identical with the properties of the standard plenoptic cameras.
All conventional plenoptic cameras suffer from the following disadvantage. While the focal depth can be increased with the standard setup, any improvement of the effective resolution of the plenoptic camera is limited by the number of microlenses used.